sync with head.
for a reference, the tree before this commit was tagged
as yamt-pagecache-tag8.
this commit was splitted into small chunks to avoid
a limitation of cvs. ("Protocol error: too many arguments")

Workaround a toolchain issue by renaming the 'setup' host tool to 'mkdata' to make UAC happy when building with Cygwin. As described here -- http://msdn.microsoft.com/en-us/library/windows/desktop/bb756960.aspx -- 32-bit executables whose filenames include the strings 'install', 'setup', 'update', 'patch', etc. by default will request admin privileges unless an application manifest is provided.

Rework how MAKEVERBOSE operates:
* Don't bother prefixing commands with a line of ${_MKCMD}\
and instead rely upon "make -s". This is less intrusive on
all the Makefiles than the former. Idea from David Laight.
* Rename the variables use to print messages. The scheme now is:
_MKMSG_FOO Run _MKMSG 'foo'
_MKTARGET_FOO Run _MKMSG_FOO ${.TARGET}
From discussion with Alistair Crooks.

Don't chown installed files or directories if UNPRIVILEGED is defined.
"make build" should now work as a non-root user (tested on Alpha).
mtree spits out lots of warnings during "make distrib-dirs", but
these are non-fatal.

These updates to the build allow building against include files
and libs in the object tree, if you use a separate object tree,
while maintaining backward compatability with other build methods.
See the notes in src/share/mk/bsd.README for full details. Note
that the `make includes' target now only installs the include files
in the build directory (if you use one--otherwise they go in DESTDIR
just like before); `make install' will install include files in
DESTDIR.